CN113890032B - Power electronic transformer control method and system for power quality control of transformer area - Google Patents

Power electronic transformer control method and system for power quality control of transformer area Download PDF

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Publication number
CN113890032B
CN113890032B CN202111162516.2A CN202111162516A CN113890032B CN 113890032 B CN113890032 B CN 113890032B CN 202111162516 A CN202111162516 A CN 202111162516A CN 113890032 B CN113890032 B CN 113890032B
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current
component
power electronic
electronic transformer
power
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CN113890032A (en
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程序
刘欣厚
王超
刘动
刘文龙
吕志鹏
周珊
牛垣绗
郭泰龙
袁媛
赵瑞红
米轶伦
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State Grid Corp of China SGCC
China Electric Power Research Institute Co Ltd CEPRI
State Grid Beijing Electric Power Co Ltd
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State Grid Corp of China SGCC
China Electric Power Research Institute Co Ltd CEPRI
State Grid Beijing Electric Power Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/01—Arrangements for reducing harmonics or ripples
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • H02J3/1821—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators
    • H02J3/1835—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control
    • H02J3/1842—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control wherein at least one reactive element is actively controlled by a bridge converter, e.g. active filters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/40—Arrangements for reducing harmonics

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

The invention discloses a control method and a system for a power electronic transformer for power quality control of a transformer area, wherein the method comprises the following steps: local load current i Labc Outputting a compensation current component of the reference current through a compensation current generation link; fundamental wave positive sequence active component i of grid-connected power tracking current dref The output obtained by inverse Peak conversion is added with the compensation current component to obtain the reference current i of the output current of the power electronic transformer under the two-phase static coordinate system αβref The method comprises the steps of carrying out a first treatment on the surface of the Will reference current i αβref In the input current controller, the power electronic transformer outputs a current i 2abc After being used as control feedback quantity and being subjected to park transformation, the control signal i is output under the tracking action of the current controller αβout And then, under the further action of the PWM generation link, outputting a driving signal of the IGBT in the power electronic transformer to form a control closed loop. The control method of the power electronic transformer can effectively reduce the control complexity and the electric energy quality control cost of the transformer area, and ensure the electric energy quality and safe and stable operation of the transformer area.

Description

Power electronic transformer control method and system for power quality control of transformer area
Technical Field
The invention belongs to the field of power quality control methods, and particularly relates to a power electronic transformer control method for power quality control of a transformer area.
Background
The measures for controlling the electric energy quality of the low-voltage distribution area with the distributed power supply mainly comprise passive control of the distribution area and active control of the distributed power supply. In the traditional power grid, the synchronous generator generally does not have the condition for realizing the power quality control, so that the power quality of the power distribution network can be passively controlled only by using special power quality control devices such as a power filter, a power distribution network synchronous compensator and the like. According to the different electric energy quality problems to be treated, the passive treatment of the power distribution network can be divided into two types, namely voltage passive treatment and harmonic passive treatment. The voltage level is mainly dependent on the reactive power balance in the system, so that in practice system voltage fluctuations can be effectively suppressed by reactive compensation. Common harmonic remediation devices include both passive power filters and active power filters.
In a low-voltage distribution area, along with the continuous improvement of the permeability of a distributed power supply, a power electronic transformer often cannot work under a rated output working condition, and the distributed power supply is connected to the distribution area, so that the power quality problems of voltage fluctuation, power harmonic injection, three-phase imbalance and the like are easily caused.
Disclosure of Invention
The invention aims to provide a power electronic transformer control method and system for power quality control of a transformer area, which are used for solving the problem that in the prior art, a power electronic transformer cannot work under a rated output working condition.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
a power electronic transformer control method for power quality control of a transformer area comprises the following steps:
to PCC point voltage U gabc Local load current i Labc Output current i of power electronic transformer 2abc Sampling;
the local load current i Labc Outputting a compensation current component of the reference current through a compensation current generation link;
setting the PCC point voltage U gabc Obtaining a theta angle required by park transformation through the action of a phase-locked loop; fundamental wave positive sequence active component i of grid-connected power tracking current dref And fundamental positive sequence reactive component i qref Adding the output obtained by inverse Peak conversion and the compensation current component to obtain a reference current i of the output current of the power electronic transformer under a two-phase stationary coordinate system αβref ；
The reference current i is set αβref In the input current controller, the power electronic transformer outputsCurrent output i 2abc After being used as control feedback quantity and being subjected to park transformation, the control signal i is output under the tracking action of the current controller αβout And then, under the further action of the PWM generation link, outputting a driving signal of the IGBT in the power electronic transformer to form a control closed loop.
Further, the method for calculating the compensation current component is as follows:
local load current i Labc Obtaining i through park transformation Ld And i Lq Respectively sending the signals into a low-pass filter to obtain a direct current component i Ldf And i Lqf ；
Will i Ld And i Lq Respectively with direct current component i Ldf And i Lqf The difference is made to obtain an alternating current component i in the load current under the two-phase synchronous rotation coordinate system Ldh And i Lqh ；
To the alternating current component i Ldh And i Lqh Conversion by inverse Peak transform to component i in two-phase stationary coordinate system Lαh And i Lβh And obtaining a compensation current component of the reference current.
Further, the fundamental wave positive sequence active component i of grid-connected power tracking current dref And fundamental positive sequence reactive component i qref Conversion by inverse Peak transform to component i in two-phase stationary coordinate system αqref And i βdref Component i αqref And component i Lαh Adding, component i βdref And component i Lβh Adding to obtain a reference current component i under a two-phase stationary coordinate system αref And i βref 。
Further, the power electronic transformer is a three-phase three-wire system power electronic inverter.
Further, the inverter circuit of the three-phase three-wire system power electronic inverter is composed of six insulated gate bipolar transistors S 1 ～S 6 The method comprises the steps of connecting the power distribution network to the PCC point through an LCL type filter, and finally accessing the power distribution network; a local load is connected in parallel at the PCC point.
Further, the LCL filter is three-phase symmetrical and comprises an inversion side inductor L 1 Network side inductance L 2 A filter capacitor C; the inversion side inductance L 1 Network side inductance L 2 The power electronic transformer is connected in series between the power electronic transformer and the power distribution network; the filter capacitor C and the network side inductance L 2 And are connected in parallel.
Further, a damping resistor R is connected in series on a parallel capacitor branch of the filter capacitor C.
Further, the local load current i Labc The expression of (2) is as follows:
in the method, in the process of the invention,and->The effective value and the initial phase of the n-th harmonic current positive sequence component are respectively; />And->The effective value and the initial phase of the negative sequence component of the nth harmonic current are respectively.
Further, for the local load current i Labc The park transformation is performed to obtain the expression:
in θ 0 For the included angle between the d axis and the a phase axis at the initial moment, after the three-phase load current is subjected to park transformation, only the fundamental positive sequence component is converted into direct current, and the fundamental positive sequence component in the three-phase load is extracted by using a low-pass filter, so that the residual harmonic and negative sequence components are obtained.
In another aspect of the embodiment of the present invention, a system for the power electronic transformer control method is provided, including:
sampling module for applying voltage U to PCC point gabc Local load current i Labc Output current i of power electronic transformer 2abc Sampling;
a compensation current component module for the local load current i Labc Outputting a compensation current component of the reference current through a compensation current generation link;
a reference current module for applying the PCC point voltage U gabc Obtaining a theta angle required by park transformation through the action of a phase-locked loop; fundamental wave positive sequence active component i of grid-connected power tracking current dref And fundamental positive sequence reactive component i qref Adding the output obtained by inverse Peak conversion and the compensation current component to obtain a reference current i of the output current of the power electronic transformer under a two-phase stationary coordinate system αβref ；
A driving signal module for comparing the reference current i αβref In the input current controller, the power electronic transformer outputs current i 2abc After being used as control feedback quantity and being subjected to park transformation, the control signal i is output under the tracking action of the current controller αβout And then outputting a driving signal of the IGBT in the power electronic transformer under the further action of the PWM generation link.
The beneficial effects of the invention are as follows:
1. according to the power electronic transformer control method provided by the embodiment of the invention, the power quality control function is compounded on the basis of the basic grid-connected function, and the reference current not only comprises a fundamental wave positive sequence active component, but also comprises various harmonic waves, reactive power and unbalanced components. The control complexity and the electric energy quality control cost of the transformer area can be effectively reduced, the equipment utilization rate is improved, and the electric energy quality and safe and stable operation of the transformer area are ensured.
2. Because the topological structure of the power electronic transformer used by the distributed power supply is basically the same as that of the power quality devices such as the active power filter, the power electronic transformer control method provided by the embodiment of the invention utilizes the residual capacity of the power electronic transformer to actively govern the power quality of the power distribution network. The utilization rate of the power electronic transformer in the transformer area is improved, and the control complexity and the electric energy quality management cost of the transformer area are effectively reduced.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:
fig. 1 is a connection topology diagram of a power electronic transformer and a power distribution network in an embodiment of the present invention.
Fig. 2 is a schematic diagram of a control method of a power electronic transformer according to an embodiment of the invention.
Fig. 3 is a schematic diagram of a reference current generation algorithm according to an embodiment of the invention.
Detailed Description
The invention will be described in detail below with reference to the drawings in connection with embodiments. It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other.
The following detailed description is exemplary and is intended to provide further details of the invention. Unless defined otherwise, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the invention.
In one aspect of the embodiment of the invention, a control method of a power electronic transformer for power quality control of a transformer area is provided, and a power quality control function is compounded on the basis of a basic grid-connected function. The power electronic transformer can realize rapid and accurate compensation of harmonic waves, reactive power and unbalanced components while transmitting active power, so that the electric energy quality of the power distribution network is effectively improved.
In this embodiment, in order to be able to achieve power quality management while transmitting active power. The invention provides a differential-free tracking output load current i Labc Harmonic of (a)Scheme of wave, reactive and unbalanced components, so that network current i gabc Will only contain the fundamental positive-order active component. In controlling a power electronic transformer, a reference value of an output current includes two parts: the grid-connected power tracks the fundamental positive sequence active component of the current and the compensation current. Wherein the compensation current is equal to the sum of harmonic, reactive and unbalanced components in the load current. Therefore, the control strategy of the multifunctional grid-connected inverter can be given on the basis of the main circuit topology shown in fig. 1, and the control strategy is shown in fig. 2. The specific control mode is as follows:
as shown in fig. 2 and 3, a power electronic transformer control method for power quality management of a transformer area includes the following steps:
s1, voltage U of PCC point gabc Local load current i Labc Output current i of power electronic transformer 2abc Sampling;
output current i of power electronic transformer 2abc Local load current i Labc And network current i gabc The kirchhoff current law is satisfied:
i 2abc ＝i Labc +i gabc
s2, local load current i Labc Outputting a compensation current component of the reference current through a compensation current generation link;
as shown in fig. 3, the method for calculating the compensation current component is specifically as follows:
1) Local load current i Labc Obtaining i through park transformation Ld And i Lq Respectively sending the signals into a low-pass filter to obtain a direct current component i Ldf And i Lqf . Local load current i Labc The expression of (2) is as follows:
in the method, in the process of the invention,and->The effective value and the initial phase of the n-th harmonic current positive sequence component are respectively; />And->The effective value and the initial phase of the negative sequence component of the nth harmonic current are respectively.
For local load current i Labc The park transformation is performed to obtain the expression:
in θ 0 For the included angle between the d axis and the a phase axis at the initial moment, after the three-phase load current is subjected to park transformation, only the fundamental positive sequence component is converted into direct current, and the fundamental positive sequence component in the three-phase load is extracted by using a low-pass filter, so that the residual harmonic and negative sequence components are obtained.
The result formula of park transformation is integrated in one power frequency period, the integration result of all alternating current components is zero, and the integration result of direct current components is the product of direct current components and the power frequency period. From the instantaneous reactive theory, i Lq The direct current component of (2) corresponds to the fundamental positive sequence reactive component of the three-phase load current.
2) Will i Ld And i Lq Respectively with direct current component i Ldf And i Lqf The difference is made to obtain an alternating current component i in the load current under the two-phase synchronous rotation coordinate system Ldh And i Lqh 。i Ldf And i Lqf The direct current components are obtained after the load current acts through the low-pass filter under the two-phase synchronous rotation coordinate system, and correspond to the fundamental wave positive sequence active component and the fundamental wave positive sequence reactive component of the three-phase load current respectively.
3) To the alternating current component i Ldh And i Lqh Conversion by inverse Peak transform to component i in two-phase stationary coordinate system Lαh And i Lβh As a compensation current component of the reference current. i.e Ldh And i Lqh The alternating current components in the load current under the two-phase synchronous rotation coordinate system correspond to the harmonic wave and the negative sequence component in the three-phase load current.
S3, PCC Point Voltage U gabc Obtaining a theta angle required by park transformation through the action of a phase-locked loop; fundamental wave positive sequence active component i of grid-connected power tracking current dref And fundamental positive sequence reactive component i qref Converted into a component i under a two-phase stationary coordinate system through inverse Peak conversion αqref And i βdref Component i αqref And component i Lαh Adding, component i βdref And component i Lβh Adding to obtain a reference current component i under a two-phase stationary coordinate system αref And i βref . Thereby obtaining the reference current i of the output current of the power electronic transformer under the two-phase static coordinate system αβref . Fundamental wave positive sequence active component i of grid-connected power tracking current in the invention dref Is given by the value. Wherein i is qref Positive sequence reactive component i with fundamental wave of load current Lqf Equal.
S4, the reference current i αβref In the input current controller, the power electronic transformer outputs a current i 2abc The feedback current i is obtained after park transformation as control feedback quantity αβ Outputting a control signal i under the tracking action of the current controller αβout And then, under the further action of the PWM generation link, driving signals of IGBT in the power electronic transformer are output to form a control closed loop, so that the output current of the power electronic transformer tracks the reference current without difference.
As shown in fig. 1, the main circuit controlled by the invention is the same as a traditional three-phase three-wire system LCL type power electronic transformer, and no zero sequence component exists in the system, so that the unbalanced component is only a negative sequence component. Wherein U is dc Is a direct current power supply, C 1 And C 2 Is a direct current voltage stabilizing capacitor. The power electronic transformer is a three-phase three-wire power electronic inverter.
The inverter circuit of the three-phase three-wire system power electronic inverter consists of six insulated gate bipolar electrodesTransistor S 1 ～S 6 The method comprises the steps of connecting the power distribution network to the PCC point through an LCL type filter, and finally accessing the power distribution network; and the PCC point is connected with a three-phase load in parallel and is used for simulating the influence of the local load on the network side power quality. In a three-phase half-bridge inverter circuit, the drive signals of two IGBTs of the same phase are theoretically complementary. However, in practical situations, the total on time of two IGBTs of the same phase is smaller than one period, so as to prevent the two IGBTs of the same phase from being short-circuited due to simultaneous conduction of false operations during the phase change process. In the field of power electronics, the time when two switching elements of the same phase are simultaneously turned off at the time of commutation is called dead time. The introduction of dead time can lead the waveform of the current output by the inverter to contain a certain amount of low-order harmonic waves, so that the invention adds a filter at the outlet of the inverter circuit to eliminate the pollution of high-frequency harmonic waves to the power grid.
The LCL filter used in FIG. 1 has three-phase symmetry and comprises an inversion side inductance L 1 Network side inductance L 2 A filter capacitor C; inverter side inductance L 1 Network side inductance L 2 The power electronic transformer is connected in series between the power electronic transformer and the power distribution network; filter capacitor C and net side inductance L 2 And are connected in parallel. The parallel capacitor branch of the filter capacitor C is connected with the damping resistor R in series, so that resonance peaks of the LCL third-order filter system can be effectively restrained, and resonance connection between a local load and the LCL filter is weakened, and the stability of the system is effectively improved.
In another aspect of the present invention, there is provided a system for a power electronic transformer control method, comprising:
sampling module for applying voltage U to PCC point gabc Local load current i Labc Output current i of power electronic transformer 2abc Sampling;
compensation current component module for local load current i Labc Outputting a compensation current component of the reference current through a compensation current generation link;
a reference current module for applying PCC point voltage U gabc Obtaining a theta angle required by park transformation through the action of a phase-locked loop; fundamental wave positive sequence active component i of grid-connected power tracking current dref The output obtained by inverse Peak conversion is added with the compensation current component to obtain the reference current i of the output current of the power electronic transformer under the two-phase static coordinate system αβref ；
A driving signal module for outputting a reference current i αβref In the input current controller, the power electronic transformer outputs a current i 2abc After being used as control feedback quantity and being subjected to park transformation, the control signal i is output under the tracking action of the current controller αβout And then outputting a driving signal of the IGBT in the power electronic transformer under the further action of the PWM generation link.
It will be appreciated by those skilled in the art that the present invention can be carried out in other embodiments without departing from the spirit or essential characteristics thereof. Accordingly, the above disclosed embodiments are illustrative in all respects, and not exclusive. All changes that come within the scope of the invention or equivalents thereto are intended to be embraced therein.

Claims (8)

1. The power electronic transformer control method for the power quality management of the transformer area is characterized by comprising the following steps of:
to PCC point voltage U gabc Local load current i Labc Output current i of power electronic transformer 2abc Sampling;
the local load current i Labc Outputting a compensation current component of the reference current through a compensation current generation link;
setting the PCC point voltage U gabc Obtaining a theta angle required by park transformation through the action of a phase-locked loop; fundamental wave positive sequence active component i of grid-connected power tracking current dref And fundamental positive sequence reactive component i qref Adding the output obtained by inverse Peak conversion and the compensation current component to obtain a reference current i of the output current of the power electronic transformer under a two-phase stationary coordinate system αβref ；
The reference current i is set αβref In the input current controller, the power electronic transformer outputs current i 2abc As a control feedback quantity through park transformationAfter the conversion, a control signal i is output under the tracking action of the current controller αβout Then, under the further action of the PWM generation link, driving signals of IGBT in the power electronic transformer are output;
the method for calculating the compensation current component comprises the following steps:
local load current i Labc Obtaining i through park transformation Ld And i Lq Respectively sending the signals into a low-pass filter to obtain a direct current component i Ldf And i Lqf ；
Will i Ld And i Lq Respectively with direct current component i Ldf And i Lqf The difference is made to obtain an alternating current component i in the load current under the two-phase synchronous rotation coordinate system Ldh And i Lqh ；
To the alternating current component i Ldh And i Lqh Conversion by inverse Peak transform to component i in two-phase stationary coordinate system Lαh And i Lβh Obtaining a compensation current component of the reference current;
fundamental wave positive sequence active component i of grid-connected power tracking current dref And fundamental positive sequence reactive component i qref Conversion by inverse Peak transform to component i in two-phase stationary coordinate system αqref And i βdref Component i αqref And component i Lαh Adding, component i βdref And component i Lβh Adding to obtain a reference current component i under a two-phase stationary coordinate system αref And i βref 。
2. The method for power electronic transformer control for district power quality control according to claim 1, wherein the power electronic transformer is a three-phase three-wire power electronic inverter.
3. The method for controlling a power electronic transformer for district power quality control according to claim 2, wherein the inverter circuit of the three-phase three-wire power electronic inverter is composed of six insulated gate bipolar transistors S 1 ～S 6 Is connected to PCC point via LCL filter, and finally is connected to the distributionA power grid; a local load is connected in parallel at the PCC point.
4. A power electronic transformer control method for district power quality control as claimed in claim 3, wherein the LCL-type filter is three-phase symmetrical, comprising an inverter-side inductance L 1 Network side inductance L 2 A filter capacitor C; the inversion side inductance L 1 Network side inductance L 2 The power electronic transformer is connected in series between the power electronic transformer and the power distribution network; the filter capacitor C and the network side inductance L 2 And are connected in parallel.
5. The method for controlling a power electronic transformer for district power quality control according to claim 4, wherein a damping resistor R is connected in series to the parallel capacitive branch of the filter capacitor C.
6. The method for power electronic transformer control for district power quality management according to claim 1, characterized by a local load current i Labc The expression of (2) is as follows:
in the method, in the process of the invention,and->The effective value and the initial phase of the n-th harmonic current positive sequence component are respectively; />And->The effective value and the initial phase of the negative sequence component of the nth harmonic current are respectively.
7. The method for power electronic transformer control for district power quality control according to claim 6, wherein for local load current i Labc The park transformation is performed to obtain the expression:
in θ 0 For the included angle between the d axis and the a phase axis at the initial moment, after the three-phase load current is subjected to park transformation, only the fundamental positive sequence component is converted into direct current, and the fundamental positive sequence component in the three-phase load is extracted by using a low-pass filter, so that the residual harmonic and negative sequence components are obtained.
8. A system for the power electronic transformer control method of claim 1, comprising:
sampling module for applying voltage U to PCC point gabc Local load current i Labc Output current i of power electronic transformer 2abc Sampling;
a compensation current component module for the local load current i Labc Outputting a compensation current component of the reference current through a compensation current generation link;
a reference current module for applying the PCC point voltage U gabc Obtaining a theta angle required by park transformation through the action of a phase-locked loop; fundamental wave positive sequence active component i of grid-connected power tracking current dref And fundamental positive sequence reactive component i qref Adding the output obtained by inverse Peak conversion and the compensation current component to obtain a reference current i of the output current of the power electronic transformer under a two-phase stationary coordinate system αβref ；
A driving signal module for comparing the reference current i αβref In the input current controller, the power electronic transformer outputs current i 2abc After being subjected to park transformation as control feedback quantity, the feedback quantity is output under the tracking action of a current controllerOutput control signal i αβout Then, under the further action of the PWM generation link, driving signals of IGBT in the power electronic transformer are output;
the method for calculating the compensation current component comprises the following steps:
local load current i Labc Obtaining i through park transformation Ld And i Lq Respectively sending the signals into a low-pass filter to obtain a direct current component i Ldf And i Lqf ；
Will i Ld And i Lq Respectively with direct current component i Ldf And i Lqf The difference is made to obtain an alternating current component i in the load current under the two-phase synchronous rotation coordinate system Ldh And i Lqh ；
To the alternating current component i Ldh And i Lqh Conversion by inverse Peak transform to component i in two-phase stationary coordinate system Lαh And i Lβh Obtaining a compensation current component of the reference current;
fundamental wave positive sequence active component i of grid-connected power tracking current dref And fundamental positive sequence reactive component i qref Conversion by inverse Peak transform to component i in two-phase stationary coordinate system αqref And i βdref Component i αqref And component i Lαh Adding, component i βdref And component i Lβh The sum of the two is added up,
obtaining a reference current component i under a two-phase stationary coordinate system αref And i βref 。
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